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thermostatic radiator valves

Hollis Member Posts: 105
Any recommendation for a thermostatic steam radiator valve that one can set at a certain temp and "lock" into place so that a tenant can't play with it? (at least easily)

Also how does it work as I would think the heat from the radiator has to effect it,..do they have a remote mounted  sensor?


  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    Can you just take the handle off?

    A friend had that problem with a gas stove that she wanted to protect from her three year old granddaughter. The knobs were right on the front of the stove. She needed a low-tech low-cost solution and we decided just to take the knobs off. The grandmother could put the knobs on when she needed to use the stove, and the g.d. was not strong enough to turn the valve shafts with her fingers.
  • trvs and tennants

    trv's have no control over the firing of the boiler. a tennant who is too cold, will be just as cold after the installation. trv's can only control the over heating of individual radiators. likewise they cannot prevent the boiler from firing.

    if the radiators are overheating, then that may signal a steam system problem. i would spend the trv money on checking over the system, and perhaps installing a new control system, either  outdoor reset, and several indoor sensors.

    get all radiators receiving steam at the same time, and running at 8 oz, and you should reduce hotspots. any that are left can then be controlled with a trv.--nbc
  • Hollis
    Hollis Member Posts: 105

    Well its a 7 unit apt building and all the units are pretty close in balance but the top apt is all over the place despite playing with reg vent valves. Mainly too  hot. I was thinking at least it would shut off when reaching 72 or so so there wouldn't be constant open windows in the winter. We have tried slower reg valves and because the dynamics of this apt and its insulation, (lots) its either too hot or cold. I really don't want to mess with anything with other factors because it has taken a lot of effort to get the rest of the units in line. I think once this well insulated unit gets to temp,..the reg boiler firing will allow it the themostatic valves to be charged enough to keep it close to that temp...(?)
  • trv's ?

    if the steam arrives at all the rads on a given floor at the same time, then you are in balance. i don't see why one unit gets steam before the others,unless the MAIN vents are out of balance, or the thermostat is in a draft. when you are measuring this, disregard the room temp-measure the radiator temp, and all should get equally hot at the same time if all the mains are in balance. therefore, the rooms also should all get equally hot. if not then you must be paying the fuel company to push some of the air out, instead of allowing it to escape on it's own for free!

    there is one other method of regulation: drill the air vent hole at a lower height so that the radiator will still have air in it when the vent closes. that would decrease the output by 15% or so. trv's are not cheap, so make sure that all other problems have been solved before installing them.--nbc
  • Jamie Hall
    Jamie Hall Member Posts: 23,275
    The key thing here

    is that if you have one apartment which is consistently too hot, then you really have a pretty simple problem to solve.  You can either go the TRV route, which as Nick notes is a little expensive (but they do work) or, assuming that this is a two pipe or vapour system, simply partly close the valves on the offending radiators.  You will be surprised, by the way, as to how far closed they need to be to make a difference.  Then take the handles off and hide them somewhere.  Where you can find them again.

    However, if the apartment is not consistently too hot, that won't work.  A TRV cannot make a space warmer; only cooler.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • jacksonpollack
    jacksonpollack Member Posts: 12
    I like and use TRV's

    I have has great success with TRV's once I have a building well vented in all the mains.

    Perhaps you have a cold blooded tenant who likes to keep their place at 60 degrees(many of mine do) am I going to argue with them and make them open a window in February just so I can brag about how balanced my building is and how all of my units come up to 72 degrees at the same time? Not smart.

    I like DanFoss brand TRV's they have a big white knob that has a frost through I think 80 degree setting, you can restrict the movement of the knob to a min and max range, which is what I do. I restrict the max to 72 degrees and they can put the min to 45 degrees if they want to.

    The only problem with them is they are fragile, a huge body held on the radiator with a small brass tube and if you have careless tenants they can break them off , then you much easyout the brass tube from the radiator and buy a new TRV. Tell them that the repair bill and parts will be $150-200 and they tend to be a bit more careful.

    They come in three parts: the chrome body, the steam vent, and the controller(there are several types, I like the big white knob with the numbers, this is intuative for the tenants and has held up well over the years.)

    Don't install them in the apartment that has the thermostat!!!

    The whole package of all three parts should be around $100-120. They payed for themselves in the first half of one heating season for me.
  • FJL
    FJL Member Posts: 354
    TRV Help

    I would like to install some TRV in my apt.  I discussed TRVs in a thread in the prior wall, but don't know if there is a way to find that thread.  In any event, I seem to recall something about a vacuum release or control; to make sure the TRV has one of those.  If someone who is familar with TRVs can cover this.  And I'll need to buy a different kind of vent, one that is vertical?  Thanks. 
  • Unknown
    edited October 2009
    TRVs (with vacuum)

    There are several types of TRVs available and you need to get the proper model  to match your type of heating system. Since you mention "vacuum" I'm assuming you have a 1 pipe steam system.  On a 1 pipe steam system the TRV is installed between the radiator and the radiator vent.  When the temperature of the room is below the temperature setting on the TRV, the TRV is open and the air passes through it and then out through the radiator vent. This allows steam to enter the radiator and warm the room.  When the room reaches the set TRV temperature, the TRV closes and doesn't allow the air to escape through the vent.

    The reason a vacuum breaker is needed is to allow air back into the radiator when the boiler cycles so that the next time the boiler produces steam, the closed TRV doesn't allow the air to escape from the radiator and therefore steam can't enter the radiator. Without the steam in the radiator, the room cools until it is below the set temperature on the TRV  at which time the TRV valve opens.  The air is then able to escape through the vent  and steam is allowed in the the radiator again.

    The vacuum valve is external on the Macon and internal on the Danfoss.  The radiator vent used with a TRV is an ordinary straight radiator vent. It needs to be straight rather than the standard one used on a radiator (a 90 degree vent) as it attaches to the TRV and needs to be in the vertical plane.

      Again make sure you get the correct model TRV for 1 pipe steam if that is your system.

    Here are links to :





    - Rod
  • FJL
    FJL Member Posts: 354
    One Pipe

    Thanks.  I do have a one pipe system.  I'm going to try danfoss and see how it goes.  
  • jacksonpollack
    jacksonpollack Member Posts: 12
    Yes, they have a vacuum break


    Your explanation is almost right about the reason for the vacuum break on a TRV. The main problem is that if you don't have one when the steam that is in the radiator condenses it forms a vacuum, if the TRV does not allow air back into the radiator at that point then the vacuum pulls more steam into the radiator and continues to add heat to the room, even if the TRV is up to temp and is not venting.

    So the room gets hotter.  With the incredible reduction in volume that happens when steam goes to liquid this cycle of condensing and refilling with steam could happen many times and would defeat the purpose of the TRV. This especially happens in big apartment buildings that need to fire for a long time to get all of the rooms up to temperature.

    And Yes, Danfoss's TRV's have a vacuum break and this only applies to 1-pipe systems (or two pipe vented systems, which seem to have been all the rage around where I live, Central PA.) So if the radiator has an air vent use the TRV that screws into the air vent hole and has a vent on it. Not the kind that goes in place of or next to the on/off floor valve like some HVAC hack tried to tell me I was supposed to use. Just because your radiator has "Two" pipes going in and out, does not mean you have "two" pipe system, at least not the kind that everyone talks about. If you have an air vent (and it was supposed to have one) than you have a two pipe "vented" system and you should treat it more like a one pipe system. Hope that makes sense and it probably does not apply to your situation anyways, so sorry for any confusion. But this bit of knowledge would have saved me a lot of headache in my early learning days.
  • jacksonpollack
    jacksonpollack Member Posts: 12
    Yes and No


    The link to situation is what I mean when I talked about the radiator is supposed to have a vent on it. Clearly these are not, they are what I mean by a true two pipe system.

    I have almost no experience with true two pipe steam systems, the kind with a trap on it. I can spot a trap and if I see one I know I have to pull out Holohan's Lost art of steam heating, because I never see or work on them and thus don't have a clue about them. Don't ask me why, they don't seem to install them on residential or smaller commercial(10 and under units) buildings in my area and I only work on systems in buildings that I own or on friend's homes. These are buildings built 1880's to 1940's, many retrofits that only had stoves/fireplaces originally.

    The two pipe steam system that I see a great deal of is the two pipe vented system. Holohan's Lost Art book has a diagram of it somewhere inside, I don't remember where.

    Basically the supply goes in one side of the radiator and then drips out of the other side and straight down into a wet return down in the basement. I think the return must always be wet to prevent the steam from shooting up into other radiators and causing heating problems. Also if you don't have a wet return then the TRV can be by passed since the return line can become a vent for the radiator. I have had this problem before since some of the buildings are on a much smaller, newer boiler since the original piping was installed and the water line is lower. The installer would have not cared much since all of the radiators would have gotten hot, but for me it defeated the purpose of the TRV being installed. Typically I installed a gooseneck or other method to create a false water line.

    I think the whole idea of the two pipe vented is you don't need anything fancy, i.e traps only pipes and radiators, not much to break and you can use supply pipes that are much smaller since you don't have the condensate flowing in them.

    The only problem is that you can't throttle them like a true two pipe system, but that is where the TRV comes in.

    Hope that all makes sense I am rambling all over the place with this response.
  • FJL
    FJL Member Posts: 354
    I Just Bought TRVs . . .

     I got the Danfoss for 1 pipe steam.  I can't get the grey cap off of the valve.  It screws to loosen, but won't come off.  Can I just break it off or is there some trick to getting it off.   Sorry for the dumb question, LOL.
  • Unknown
    edited October 2009
    Danfoss TRV

    Not quite sure exactly what you are referring to so I've attached two Danfoss  tech. bulletins on the Danfoss 1 Pipe steam TRV which might be of help to you.

    1. Basically all you have to do is remove the old radiator vent from the radiator (of course make sure the steam system is off and cold first- steam burns are NO fun!)

    2. Add a straight radiator vent to the TRV

    3. Thread the new TRV with vent assembly into the 1/8 FPT vent hole where you removed the old radiator vent. Use teflon tape on the threads

    Note: An air vent which attaches to the TRV isn't supplied with the Danfoss TRV.  You can use the vent Danfoss manufactures (Part # 013L9011) or use a vent from another manufacturer. The only requirement is that it is a straight vent rather than being a 90 degree vent.

    - Rod
  • FJL
    FJL Member Posts: 354
    edited October 2009
    The Grey Cap

    I understand everything that you wrote.  What I'm talking about is the grey cap that is on the valve when it come out of the Danfoss box.  It is the cap that must be removed before attaching the valve mounted dial and sensor.  You can see the grey cap on the first page of the data sheet, in the box that says "use air vent plus 1/8 one-pipe steam valve."  I assume the grey can protects the part of the valve that receives the dial and sensor.  I can't figure out how to get that grey cap off.  Once I do that, then I can attach the dial and sensore and my Gorton 6 valve.  As I said, I can unscrew it to a point, but then I won't unscrew any further.  I just don't want to force it off and possible damage the danfoss valve.  I hope that is clearer.
  • Gray Cap

    I haven't installed a Danfoss is several years and I can't remember a gray cap. It maybe that the supplier put the parts together before I picked them up as I ordered them in a special configuration (tamper proof)

    It would seem to me that if the operator is supplied separately,  the "gray cap" has to be a protective cap to protect the valve pin (See attached  picture - I blew it up a bit for detail)  The gray cap probably just snaps on. Try prying up evenly from both sides and it should pop off.  Sorry I can't offer more help than that.
  • FJL
    FJL Member Posts: 354
    Protecting the Pin

    You are correct.  The grey cap is there to protect the pin.  I'll fiddle with it and find a way to get it off.  Thanks.
  • jacksonpollack
    jacksonpollack Member Posts: 12
    correct protective cap and crappy operator

    Yes, I think most people look at the gray cap as a protective device. I think it can also be screwed in to operate the TRV, though it would be a trial and error to get the temp. right.

    Just grab onto the gray cap and pull. It is just held on by plastic fingers in a groove. Unless you somehow bend or hit the pin hard I don't you could harm much on the TRV without trying.

     I have a whole box of the things in my store room. I don't know why I kept them. Probably a pack rat landlord quanlity. I also figured if the controller ever died I could reinstall the gray cap for a short term fix.
  • FJL
    FJL Member Posts: 354

    Thanks. Finally got.  Feel so dumb.  It was so easy.  
  • Gray Cap

    It's not dumb to be cautious. Far`better to be cautious than make an expensive mistake!
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